This invention is generally directed to photoconductive imaging members, and more specifically to imaging members with polycarbonate overcoatings. The present invention in one embodiment is directed to layered photoconductive imaging members, or photoconductors, comprised of a photogenerating layer, a charge transport layer in contact therewith, and a protective overcoating layer comprised of the polycarbonates illustrated herein. The aforementioned polycarbonates in embodiments of the present invention have incorporated therein polyfluorosiloxane telomers, thereby lowering the surface energy of the photoconductor and enabling, for example, superior release of the developed image with such polycarbonates. Disadvantages of toner and paper sticking to the photoconductor can be eliminated or minimized with the overcoatings of the present invention. Other advantages of the photoconductors of the present invention reside in the reduction of the surface energy of a photoreceptor which results in lower abrasive wear of the photoreceptor surface and preserves the designed thickness of the charge transport layer; a reduction in the charge transport layer thickness can lower the ability of the photoreceptor to accept charge, thereby lowering the contrast potential and reducing the quality of the developed image. In a specific embodiment, the present invention relates to layered imaging members comprised of a supporting substrate, such as aluminum, a photogenerating layer in contact therewith, a hole transport layer, and in contact with the hole transport layer a polycarbonate having incorporated therein polyfluorosiloxane telomers during, for example, the preparation by melt esterification. The charge, especially hole, transport layer can be in contact with the overcoating layer of the imaging member, or alternatively it may be situated between the supporting substrate and the photogenerating layer. The aforementioned polycarbonates can possess a number of advantages including, for example, resistance to abrasion, excellent tensile toughness characteristics, the solubility thereof in a number of solvents such as aromatic solvents including toluene, tetrahydrofuran, xylene, and benzene, and aliphatic solvents such as halogenated hydrocarbons thus permitting, for example, improved coatability thereof with organic charge transport components utilizing various known processes such as spray, dip, and draw-down coating. Tensile toughness represents the area of a stress strain curve when a sample of the material is strained to its breaking point, this phrase being well known in the art, and moreover there can be selected a known tensile test for films and coatings of the polycarbonate binders, which tests are capable of enabling the calculation of the Young's modulus, tensile strength, yield strength, percent elongation, and tensile toughness.
The novel polycarbonates illustrated herein may also be selected in an embodiment of the present invention as a resin binder for the charge generating layer, particularly since it is believed that such a binder may enable improved photogenerating pigment dispersion stability, and increased photosensitivity for the resulting imaging member.
The imaging members of the present invention can be selected for a number of imaging and printing processes including electrophotographic imaging and printing processes for an extended number of imaging cycles, exceeding 200,000 for example, while substantially avoiding or minimizing abrasion thereof. Also, the imaging members of the present invention can be selected for a number of color imaging and printing processes.
The formation and development of electrostatic latent images on the imaging surfaces of photoconductive materials by electrostatic means is well known. Numerous different photoconductive members for use in xerography are known such as selenium, alloys of selenium, layered imaging members comprised of aryl amine charge transport layers, reference U.S. Pat. No. 4,265,990, and imaging members with charge transport layers comprised of polysilylenes, reference U.S. Pat. No. 4,618,551. The disclosures of the aforementioned patents are totally incorporated herein by reference. With the aforementioned imaging members, especially those of the '990 patent, there can be selected aryl amine charge transport layers, which aryl amines are soluble in halogenated hydrocarbons such as methylene chloride. Further, the polycarbonates of the present invention can also be selected as overcoatings for the imaging members with electron transport layers, reference U.S. Pat. No. 4,474,865, the disclosure of which is totally incorporated herein by reference.
In U.S. Pat. No. 4,869,988 and U.S. Pat. No. 4,946,754, the disclosures of which are totally incorporated herein by reference, there are described layered photoconductive imaging members with transport layers incorporating, for example, biarylyl diarylamines, N,N-bis(biarylyl)anilines, and tris(biarylyl)amines as charge transport compounds. In the abovementioned patents, there are disclosed improved layered photoconductive imaging members comprised of a supporting substrate, a photogenerating layer optionally dispersed in an inactive resinous binder, and in contact therewith a charge transport layer comprised of the abovementioned charge transport compounds, or mixtures thereof dispersed in resinous binders.
Examples of specific hole transporting components disclosed in the '988 patent include N,N-bis(4-biphenylyl)-3,5-dimethoxyaniline (Ia); N,N-bis(4-biphenylyl)-3,5-dimethylaniline (Ib); N,N-bis(4-methyl-4'-biphenylyl)-3-methoxyaniline (Ic); N,N-bis(4-methyl-4'-biphenylyl)-3-chloroaniline (Id); N,N-bis(4-methyl-4'-biphenylyl)-4-ethylaniline (Ie); N,N-bis(4-chloro-4'-biphenylyl)-3-methylaniline (If); N,N-bis(4-bromo-4'-biphenylyl)-3,5-dimethoxy aniline (Ig); 4-biphenylyl bis(4-ethoxycarbonyl-4'-biphenylyl)amine (IIa); 4-biphenylyl bis(4-acetoxymethyl-4'-biphenylyl)amine (IIb); 3-biphenylyl bis(4-methyl-4'-biphenylyl)amine (IIc); 4-ethoxycarbonyl-4'-biphenylyl bis(4-methyl-4'-biphenylyl)amine (IId); and the like.
Examples of specific hole transporting compounds disclosed in U.S. Pat. No. 4,946,754 include bis(p-tolyl)-4-biphenylylamine (IIa); bis(p-chlorophenyl)-4-biphenylylamine (IIb); N-phenyl-N-(4-biphenylyl)-p-toluidine (IIc); N-(4-biphenylyl)-N-(p-chlorophenyl)-p-toluidine (IId); N-phenyl-N-(4-biphenylyl)-p-anisidine (IIe); bis(m-anisyl)-4-biphenylylamine (IIIa); bis(m-tolyl)-4-biphenylylamine (IIIb); bis(m-chlorophenyl)-4-biphenylylamine (IIIc); N-phenyl-N-(4-biphenylyl)-m-toluidine (IIId); N-phenyl-N-(4-bromo-4'-biphenylyl)-m-toluidine (IVa); diphenyl-4-methyl-4'-biphenylylamine (IVb); N-phenyl-N-(4-ethoxycarbonyl-4'-biphenylyl)-m-toluidine (IVc); N-phenyl-N-(4-methoxy-4'-biphenylyl)-m-toluidine (IVd); N-(m-anisyl)-N-(4-biphenylyl)-p-toluidine (IVe); bis(m-anisyl)-3-biphenylylamine (Va); N-phenyl-N-(4-methyl-3'-biphenylyl)-p-toluidine (Vb); N-phenyl-N-(4-methyl-3'-biphenylyl)-m-anisidine (Vc); bis(m-anisyl)-3-biphenylylamine (Vd); bis(p-tolyl)-4-methyl-3'-biphenylylamine (Ve); N-p-tolyl-N-(4-methoxy-3'-biphenylyl)-m-chloroaniline (Vf), and the like. The aforementioned charge, especially hole transport components, can be selected for the imaging members of the present invention in embodiments thereof.
It is also indicated in the aforementioned patents that there may be selected as resin binders for the charge transport molecules those components as illustrated in U.S. Pat. No. 3,121,006 including polycarbonates, polyesters, epoxy resins, polyvinylcarbazole; and also wherein for the preparation of the charge transport layer with a polycarbonate there is selected methylene chloride as a solvent.
There is also mentioned as prior art U.S. Pat. Nos. 4,657,993, the disclosure of which is totally incorporated herein by reference, directed to polyphosphazene homopolymers and copolymers of the formula as recited, for example, in the Abstract of the Disclosure, which components may be selected as photoconductive materials and for other uses, see column 1, and continuing on to column 2; 3,515,688 related to phosphonitrile elastomers, reference for example the Abstract of the Disclosure; 3,702,833 directed to curable fluorophosphazene polymers, see for example column 1; and 3,856,712 directed to polyphosphazene copolymers which are elastomers; and 4,921,940. The disclosures of each of the aforementioned patents are totally incorporated herein by reference.
In copending application U.S. Ser. No. 546,821 (D/90084), the disclosure of which is totally incorporated herein by reference, there is illustrated a layered photoconductive imaging member comprised of a supporting substrate, a photogenerating layer comprised of organic or inorganic photoconductive pigments optionally dispersed in an inactive resinous binder, and in contact therewith a charge transport layer comprised of the aryl amines as illustrated in U.S. Pat. Nos. 4,265,990; 4,464,750 and 4,921,773, the disclosures of which is totally incorporated herein by reference, which amines can be dispersed in a block copolymer resin binder of the formula: ##STR2## wherein R.sub.1, R.sub.2, and R.sub.3 are independently selected from the group consisting of hydrogen, alkyl, and aryl; and k, j, m, and n represent the number of repeating units. The polycarbonatefluorosiloxane polymers of the present invention are believed to possess excellent release characteristics as indicated herein as compared to the aforementioned block copolymers of the U.S. Ser. No. 546,821 patent application.
While imaging members with various overcoatings are disclosed in the prior art, and are suitable for their intended purposes, there continues to be a need for improved imaging members, particularly layered members, with abrasion resistant surfaces. Another need resides in the provision of layered imaging members that are compatible with liquid developer compositions. Further, there continues to be a need for layered imaging members wherein the layers are sufficiently adhered to one another to allow the continuous use of such members in repetitive imaging systems. Also, there continues to be a need for improved layered imaging members comprised of hole transport layers wherein the problems of transport molecule crystallization, bleeding and leaching are avoided or minimized. Furthermore, there is a need for imaging members with protective overcoatings whereby there is enabled excellent toner image release therefrom, and wherein the photoconductor abrasion is avoided or minimized. A further need resides in the provision of photoconductive imaging members with desirable mechanical characteristics. A further need resides in providing for improved paper stripping from the photoreceptor surface.